Currently, to ensure that an electrical power facility such as a data center can save and process data in the event of a power failure, an uninterruptible power supply (UPS) is generally used to provide backup power. A conventional UPS supports two-stage power conversion in which an alternating current mains is rectified into a high-voltage direct current to charge a battery, and then a direct current output by the battery is converted into an alternating current to supply power to the electrical power facility. However, as power of a facility continuously increases, power consumption in a two-stage power conversion process also increases. Therefore, currently, in an increasing number of solutions, a later stage, that is, a conversion part of a UPS is eliminated, and a high-voltage direct current is directly used to supply power to an electrical power facility.
Currently, in all electrical power facilities, alternating current rectifiers are used, and relays in the alternating current rectifiers have excellent alternating current breaking capacities, but have relatively poor direct current breaking capacities. Under a condition of direct current input, an arc flash may be caused when a current-carrying relay is disconnected. Therefore, under a condition of direct current input, when a relay is faulty, the relay is disconnected when carrying a current, which causes an arc fire to the relay, thereby resulting in a problem of poor security.